Shielded antenna feeder lead or line



J ne 29,. 1943. H. o. ROOSENSTEIN.

SHIELDED ANTENNA FEEDER LEAD OR LINE Filed Dec. 21, 1940 INVENTOR HANS 0. RfgNSTE/N ATTORNEY Patented June 29, 1943 SHIELDED ANTENNA FEEDER LEAD OB LINE Hans Otto ltoosenstein, Berlin, Germany: vested in the Alien l'roperty Custodian Application December 21, 1940, Serial No. 371,089

In Germany April 11, 1939 2 Claims. (Cl. 178-44) This invention is concerned with a shielded an enna feeder in the form of a coaxial cable which is furnished with means adapted to suppress shell waves, that is to say, waves arising upon the outer surface of the feeder lead shield. It

is, basically, speaking, known in the artto obviate the disturbing action of waves of the said sort by branching-oil? from the feeder line auxiliary conductors which are tuned in their length and which are so arranged and dimensioned that for high-frequency waves liable to arise upon the outer shell and originating at the cable end, the impedance becomes high with the result that the cable shell, from a certain point, is..practically completely at ground potential. Arrangements designed to this end had this drawback that they were impracticable from the construction viewpoint and that they entail a good deal of expense. As a result they have failed to become generally adopted in practice. To remedy this situation, the invention creates an antenna feeder in the form of .a coaxial cable consisting of a compact cable formed by a centrally located flexible radio frequency lead with two shielding sheaths or shells being insulated from each other, the outer shell being broken at convenient points and being connected with the inner one.

Hence, the invention resides in the fact and feature that the antenna leads and the means adapted to shell wave suppression are constructionally united to form a compact and flexible radio frequency line, this oil'ering especially the advantage that. the manufacture of the whole line may proceed in one uninterrupted production stage and process without any complicated accessory steps being necessary in such manufacture.

Fundamentally speaking, radio frequency cables with double shielding sheaths or shells are nothing new in the art. What is new in the invention is to subdivide the outershell at certain places to the end of insuring 'efiective and efllcient suppression of. disturbing waves or stray waves traveling along the inner shell surface.

The inventiqn shall now be described more fully by reference to the appended drawing, in

which Fig. l is a longitudinal section of one form of a coaxial cable of this invention, Fig. 21s a cross-section of another form of coaxial cable of this invention, and Fig. 3 is a longitudinal section of still another form of this invention. Referring now in detail to the drawing:

Fig. 1 shows an antenna feeder line or cable comprising an inner conductor J which acts as radiator S, and an outer conductor A which is maintained practically at ground potential. Upon the outer conductor, and co-axial in respect to the same, are auxiliary conductors T, the latter being unilaterally connected with the outerficonductor A, while the length thereof is tuned to the working wave. If thme auxiliary conductors were to be fitted later on the radio frequency line or cable, that is, after the latter has been finished, this would be attended with essential 'difliculties both constructional and in practical use, but if for the antenna feeder lead there is employed a cable of the kind shown in cross-section 'in Fig. 2, all'of these difdculties are at once vobviated. Referring to Fig. 2, J is the inner conductor which together with the insulating "sheath or envelope DI and the inner shielding shell A| constitutes an air-insulated, flexible radio frequency cableL of a kind known in the art. The shielding shell Al is surrounded by a furtherinsulating shell D2 made of lowloss materialand insulated from the second shielding envelope A2. The entire conductor assembly is further enclosed in a rubber envelope G thus resulting in a compact flexible iliary conductors indicated at T in Fig. 1. For this purpose, it is split or subdivided at certain suitable intervals and then connected with the inner shield as shown in Fig. 1. This subdivision may be made either when the cable is being manufactured or at some later time'by cutting the rubber envelope G. This offers no particular difliculties. To make the subdivision later as last mentioned offers the advantage that one and the same shell may be used for widely varying purposes inasmuch as the length of the auxiliary conductors which is a function of the operating frequency is determined, as will be noted, only at a later date, that is, only when the feeder is installed. The number of gaps and thus the number of auxiliary conductors 'T'is wholly a function of prevailing conditions and it may be chosen so-as to suit these conditions. What is essential in this connection is that basically there is a chance to furnish the entire feeder line or cable with auxiliary conductors.

It will be understood that the invention is not confined to the exemplified embodiment shown in Fi 1. In fact, there are many instances in practice where auxiliary conductors for shell or surface wave suppression will prove, expedient of the kind illustrated in Fig. 3. These distinguish the high voltage member and terminates in the 56 themselves from the ones shown in Fig. 1 only in so far as the connec in points and the shield- Fig. 3 is applicable in the very same. manner to the cable Fig. 2 in away as hereinbeiore described.

Moreover, the invention is not restricted to the particular form or construction shown in Fig. 2. On the contrary, any other flexible form of cable known in the art with twin shielding shell may be employed; all that is necessary is to take care so that a kind of dielectric material having not unduly high losses is interposed between the two cable sheaths. I

One particular ileld of application is for antenna feeder leads or cables used in connection with television receiver installations.

What is claimed is:

l. A flexible radio frequency air insulated coaxial cable comprising an inner conductor, a first insulating sheath surrounding said inner. conductor, an outer tubular conductor, a second insulation sheath surrounding said outer conductor, and a pluralitir of tubular metallic members located outside of said insulation sheath surrounding said outer conductor, each tubular metallic member being so dimensioned as to suppress outer suriace waves and being spaced apart from one another also connected at one end thereof to said outer tubular conductor.

2. A flexible radio frequency air insulated co axial cable comprising an inner conductor, a first insulating sheath surrounding said inner conductor, an outer tubular conductor, a second insulation sheath surrounding said outer conductor, and a plurality of tubular metallic members surrounding said outer conductor, each tubular metallic member being so dimensioned as to suppress outer surface waves and being spaced apart from one another also connected at one end thereof to said outer tubular conductor, and a third outer sheath oi. rubber surrounding said tubular metallic members.

Hans o'rro noosnns'mm. 

